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Sensory Overload

If you’ve been into robotics for more than a few years, at some point you’ve probably spent hours trying to fabricate a sensor either because the best one for the job was too expensive or because one didn’t exist. You’ve probably also come to appreciate that selecting and interfacing sensors to processing gear are at least half of the equation when designing robots.

With factory robots in Japan receiving pink slips and a general surplus of sensors and other robotics components on the market, it’s become a buyer’s market. The design challenge has shifted from affordability to the best fit for a particular application.

There is a wealth of discrete sensors on the market, with accuracy and functionality for any budget. For example, I’ve been experimenting with the new Honeywell dual-axis magnetic sensors, available from the folks at SparkFun Electronics (www.sparkfun.com). The leadless SMD package is virtually impossible to work with without a good hot air pen and magnifier. If you’re limited to a soldering iron, then take a look at the thumbnail-sized breakout board, also from SparkFun.

If you’re into kits, I’ve found the products from the Australian company Oatley Electronics (www.oatleyelectronics.com) some of the best around. I’m in the middle of a project that uses their Hall-effect interface kit (see photo) which makes a great rotational speed sensor for a large robot. If you’re working with a carpet roamer, then go with the nearly microscopic Honeywell sensors. However, if you need a rugged sensor that you can service without a microscope, then take a look at the Oatley kit.

One of the best features of the Oatley product is the provision for a remote sensor. No need to expose the entire circuit to dust, dirt, and mud – simply snap off the edge of the main circuit board and connect a three-wire cable between the two boards. As with SparkFun, you can go to the Oatley website and download detailed information on these and other sensors. One of the beneficial side-effects of the game industry is renewed interest in multidimensional controllers. My favorite — the Nintendo Wii controller — is probably the most repurposed sensor in history. I’ve seen the mems harvested from these inexpensive controllers show up in everything from surgical simulators for training clinicians to exercise equipment. The strain gauge sensor in the Wii Fitness product has a strong following, as well.

From what I can see, the strongest push for cheaper, faster, more efficient sensors is coming from the smart phone industry. Smart phones in the US are starting to catch up with those in Japan, with magnetic field sensors, multi-axis accelerometers, ambient light, and distance (for shutting down the display when the phone is against your ear). Even body impedance (for body fat calculation) is the norm. Soon, it’s going to be easy enough to drop smart phones into your robot platform and instantly have a full arsenal of sensors, two-way audio and video, voice command, and world-wide control via the Internet. Someone will have to think up an alternative name for the obvious “iRobot” platform.

The nature of our relationship with sensors is changing. Well over a year ago, I retired my multi-function, sensor-laden watch with barometric pressure, temperature, direction, altitude, and chronometer in favor of my smart phone. Those old data points are insufficient. I don’t simply want direction, but direction relative to the nearest restroom or filling station. I’m not concerned with raw altitude, but my altitude relative to my surroundings. And who looks at their wrist for time anymore? Dump your watch and see how long it takes for you to stop reflexively glancing at your wrist for the time instead of at your smart phone.

The explosion in affordable sensors is a good thing. Of course, there will be an eventual consolidation of the vendors and standards, and the eventual emergence of a multi-function sensor that’s integrated into every smart appliance on the planet. At that point, your drop-in cell phone will enable your robot with GPS, face recognition, voice recognition, and a host of other features that would have once cost thousands of dollars to implement with discrete sensors. For now, enjoy the affordability and variety of the devices flooding the market. SV